The present invention relates to a photoselective absorbing filter, and to a color display device equipped with said filter. More particularly, the present invention relates to a photoselective absorbing filter wherein reflected light is controlled by reducing light transmittance at a wavelength ranging from 470 to 510 nm and at a wavelength ranging from 550 to 600 nm, while inhibiting light absorption from the display device as little as possible, and to a color display device equipped with said filter.
Color display devices, such as CRT, PDP (plasma display panel), and liquid crystal display panels, usually are provided with an antireflection filter to improve contrast. A single layer filter is particularly preferable because of ease of handling. The antireflection filter is used to prevent external light, which is incident upon a display device from the outside of the display panel, from being reflected on a picture plane of the display device, and to solve a problem wherein the picture plane of the display device becomes invisible.
The antireflection filter ideally functions to inhibit a decrease in luminance of light from red, green, and blue picture elements to a minimum, and absorbs external light as much as possible. Filters using various color materials are known.
For example, a mixed coloring material prepared by mixing a blue pigment with a red pigment, and an anhydrous phosphoric acid cobalt pigment, recently have been suggested as the coloring material used in the antireflection filter.
However, a currently suggested filter formed by mixing a blue pigment with a red pigment has a disadvantage in that the transmittance is lowered at a green color wavelength ranging from 500 to 600 nm, thereby absorbing light emitted from the green picture element, which results in a decrease in luminance.
Also in an antireflection filter using an anhydrous phosphoric acid cobalt pigment, luminance is lowered due to poor transparency, and basic quality of the filter is presently insufficient.
The present invention solves the problems described above, and an object of the present invention is to provide a photoselective absorbing filter that does not cause a decrease in luminance of a picture element in a display device, and also is capable of absorbing external light with high efficiency, and to provide a color display device equipped with said filter.
A photoselective absorbing filter of the present invention comprises a light selective absorbing coloring material that selectively absorbs external light in a color display device with blue, green, and red picture elements, characterized in that a transmittance of light at a wavelength ranging from 470 to 510 nm and at a wavelength ranging from 550 to 600 nm is smaller than a transmittance of light in the visible range (380 to 780 nm) other than said two wavelength ranges.
Usually, blue, green, and red picture elements have an emission spectrum peak at about 450 nm, 540 nm and 630 nm, respectively. However, the photoselective absorbing filter of the present invention has absorption peaks at wavelength ranges different from these three emission peaks, that is, a wavelength ranging from 470 to 510 nm and a wavelength ranging from 550 to 600 nm, such that the luminance of the light-emitting picture elements is not reduced, and, moreover, reflected light is absorbed with high efficiency.
The photoselective absorbing filter of the present invention can be used in various color display devices, such as CRT, PDP, and liquid crystal display panels.
The photoselective absorbing coloring material of the present invention preferably contains (a) a pyridinophthalocyanine selected from the group consisting of a metal-tetra-2,3-pyridinoporphyrazine represented by the general formula (I), a metal-tetra-3,4-pyridinoporphyrazine represented by the general formula (II), a tetra-2,3-pyridinoporphyrazine represented by the general formula (III), and a tetra-3,4-pyridinoporphyrazine represented by the general formula (IV), and (b) an anthraquinone dye: 
wherein M represents a center metal selected from copper, cobalt, nickel, zinc, iron, tin, and aluminum; X represents a ligand bonded directly to the center metal M and is a halogen atom, such as fluorine, chlorine, or bromine, an oxygen atom, a nitrogen atom, a hydroxy group, or a siloxane group in Chemical Formulae (I) and (II). R represents an alkyl group or a halogen atom, and n represents an integer 0 to 3 in Chemical Formulae (I)-(IV).
M is not described as a xe2x80x9ccenter metal ion,xe2x80x9d but is described as a xe2x80x9ccenter ionxe2x80x9d in the present specification because the metal tetrapyridinoporphyrazine described above did not dissociate into ions in the photoselective absorbing filter of the present invention, unlike the solution state.
Methods of preparing a pyridinophthalocyanine according to the present invention, for example, heating 2,3-dicyanopyridine, 3,4-dicyanopyridine, or a derivative thereof, together with a metal source, such as cupric chloride, and heating a metal source, such as quinolineamide, together with an ammonium salt of aminosulphonic acid, are known. However, it is more advantageous with respect to the manufacturing process and cost to use the Wyler method (e.g. xe2x80x9cPHTHALOCYANINE COMPOUNDS,xe2x80x9d Moser et al., Reinhold Publ. Co., 1963, xe2x80x9cSHINSENRYO KAGAKU (New Dye Chemistry),xe2x80x9d written by Yutaka HOSODA, Gihodo, 1963), which is a standard method of preparing a copper-phthalocyanine known as a coloring material. General raw materials used in the preparation of a metal-phthalocyanine by the Wyler method are phthalic anhydride, urea, a metal source, such as copper chloride, and a catalyst (ammonia molybdate). A pyridinophthalocyanine can be satisfactorily prepared by replacing phthalic anhydride with quinolic acid, quinolic anhydride, cinchomeronic acid, or a derivative thereof, in accordance with a method of synthesizing copperphthalocyanine, and other conditions, such as reaction temperature, time, and the like, are the same as the above Wyler method.
It is necessary to monitor the amount of raw materials, such as quinolic acid, quinolic anhydride, cinchomeronic acid, or a derivative thereof, in the same manner as in a conventional reaction, because a pyridiniophthalocyanine pigment performs an objective function of the present invention. Because a pigmentation process also is required in the same manner as in case of other conventional pigments, it is also necessary to monitor the pigmentation.
Examples of an anthraquinone dye useful in the photosensitive absorbing filter of the present invention include Solvent Orange (35, 64, 65, 66, 68, 69, 71, 77, 86, and 87) and Solvent Red (52, 152, 155, 156, 168, 169, 170, 171, 172, 175, 177, 181, 190, and 191). The numerical value in the parentheses indicates a color index.
The coloring material used to make a photoselective absorbing filter of the present invention can be prepared by forming a dispersion of a pyridinophthalocyanine, and mixing the dispersion with a solution of a anthraquinone dye. The pyridinophthalocyanine dispersant can be prepared using conventionally known devices, such as ball mill, beads mill, roll mill, ultrasonic dispersing device, and the like.
The mixing ratio of pyridinophthalocyanine to the anthraquinone dye preferably is within a range from 80:20 to 20:80, in view of the shape of a spectral transmission spectrum. When the proportion of pyridinophthalocyanine exceeds 80%, an absorption at about 480 nm is poor, and an efficient absorption of external light is impossible to attain, which is not preferable. On the other hand, when the proportion of the anthraquinone dye exceeds 80%, an absorption at about 580 nm is poor, and an efficient absorption of external light is impossible to attain, which is not preferable.